1. Field of Invention
The present device relates to a female terminal fitting for a connector, which has a cylindrical insertion portion whose front end is opened and which is connected to a mating male terminal fitting by allowing the male terminal fitting to be inserted into the cylindrical insertion portion.
2. Description of Prior Art
A connector adapted for use in connecting electrical wires is designed to attach a male terminal fitting to one of a pair of connectors to be connected to each other and a female terminal fitting to the other, and to insert the male terminal fitting to a cylindrical insertion portion of the female terminal fitting formed by opening the front end of the female terminal fitting, so that both male and female terminal fittings can be connected to each other electrically.
The female terminal fitting has the cylindrical insertion portion formed by bending a metal strip in cylindrical form and a fold formed by folding a part of the metal strip from the front end opening of the cylindrical insertion portion toward the hollow so as to depict a loose arc. A resilient contact piece that is given resiliency is disposed on the fold. One known example is a device shown in FIGS. 19, 20 which is disclosed in Japanese Unexamined Utility Model Publication No. 63-26979, and another is shown in FIG. 21. Each of these female terminal fittings 50 is constructed so that a resilient contact piece 53 extends rearward by folding the slenderly extending resilient contact piece 53 from the front end opening 52 of a cylindrical insertion portion 51 into the hollow, and causes a not shown male terminal fitting to come in contact with the female terminal fitting by clamping the male terminal fitting between the cylindrical insertion portion 51 and an inner wall 54 thereof by resiliency of the resilient contact piece 53.
Further, as shown in FIG. 22, another example, which is characterized as arranging a second fold 57 formed by folding the front end of the resilient contact piece 53 so as to depict a loose arc, is known. Exhibiting resiliency not only at a first fold 56 but also at the second fold 57 on the extended end, such doubly folded resilient contact piece 53 has an excellent spring characteristic. That is, the male terminal fitting can be inserted with ease by a small insertion force and, in addition, once the male terminal fitting has been inserted, the contact pressure is so high as to ensure excellent contact reliability.
The resilient contact piece 53 is given resiliency by bending a metal strip. Therefore, if a flexing force exceeding the limit of resiliency is applied to the resilient contact piece 53, i.e., if a foreign object that is thicker than the male terminal fitting (e.g., the tip of a screwdriver) is inserted, or if the male terminal fitting is inserted obliquely, the resilient contact piece 53 settles to lose the proper spring characteristic thereof. To prevent such settling, a stopper has heretofore been arranged on the resilient contact piece 53. In the female terminal fitting shown in FIG. 20, stoppers 60 formed by bending projecting pieces arranged on both sides of the resilient contact piece 53 perpendicularly are provided. The lower end portions thereof are abutted against the bottom surface of the cylindrical insertion portion.
The female terminal fitting shown in FIG. 21 has a stopper 61 that is prepared by forming a projection while cutting a part of the wall portion facing the back of the resilient contact piece 53 and bending such projection upward so as to correspond to the back of the resilient contact piece 53.
Another conventional terminal fitting of this type having, as shown in FIG. 23, a cylindrical contact portion 101 at the front part thereof and a crimping portion 102 for crimping an electrical wire at the rear part thereof has heretofore been known. This terminal fitting is formed cubically by first cutting a developed blank out of a flat metal strip and then bending portions of such developed blank as necessary. A bottom wall 103 of the contact portion 1 is formed by cutting with a band-like metal piece left in the front and by bending the rear end thereof upward, so that the bank-like metal piece forms a flexible tongue piece 4 that projects from the bottom wall side to the ceiling wall side within the cylinder. The flexible tongue piece 104 is designed to cause a male terminal fitting to be biased onto the ceiling wall when the male terminal fitting is inserted into the cylinder. On the other hand, a reinforcing piece 105 that is formed by cutting the middle portion of the bottom wall 101 and bending the cut piece upward is designed to prevent the flexible tongue piece 104 from flexing excessively downward.
Still further, another conventional female terminal fitting for a connector which is attached to the connector and connected to a male terminal fitting of a mating connector is shown in FIG. 24. This female terminal fitting 340 is fabricated by bending a metal strip piece punched into a predetermined shape, and has a cylindrical insertion portion 341 whose front end is opened serving as an insertion opening 342. A resilient contact piece 345 is disposed within the cylindrical insertion portion 341. The resilient contact piece 345 is given resiliency by a fold 345a with a portion slenderly extending from the front end of a lower wall plate 343 constituting the cylindrical insertion portion 341 folded rearward. The thus constructed female terminal fitting 340 is inserted into a cavity 351 formed in a connector 350 from the rear and unreleasably attached to the connector 350 by a lance 353 with an insertion opening 342 thereof aligned with a connecting opening 352 formed at the front end of the connector 350.
At the time the female terminal fitting 340 attached to the connector 350 is connected to the male terminal fitting attached to the mating connector (not shown), a tab 355 projecting from the front end of the male terminal fitting enters into the cylindrical insertion portion 341 while sequentially passing through the connecting opening 352 and the insertion opening 342 of the female terminal fitting. Then, the tab 355 is then clamped between the upper surface of the resilient contact piece 345 and the upper wall surface 346 of the cylindrical insertion portion 341, both surfaces as viewed in FIG. 24, by resiliency of the resilient contact piece 345. As a result, the male terminal fitting is reliably connected electrically to the female terminal fitting 340.
In the aforementioned connecting means the connecting opening 352 of the connector 350 has so large an opening as to allow the tab 355 of the male terminal fitting to be releasably inserted, whereas the insertion opening 342 of the cylindrical insertion portion 341 has an opening larger than that of the connecting opening 352 so as to be opened over almost all the front end surface of the cylindrical insertion portion 341.
As a result, a foreign object such as, e.g., the tip of a screwdriver which is thicker than the tab 355 may, in some cases, be inserted into the cylindrical insertion portion 341 from the connecting opening 352, or the tab 355 may be inserted obliquely as shown in FIG. 24. In such a case, the fold 345a of the resilient contact piece 345 flexes to such a degree as to exceed the limit of resiliency thereof and settling occurs due to such excessive flexion, so that the proper spring characteristic of the resilient contact piece 345 is lost. Once the proper spring characteristic has been lost, the resilient contact piece 345 cannot clamp the inserted tab 355 together with the upper wall surface 346 at a predetermined contact pressure, thus not providing reliable contact between the male terminal fitting and the female terminal fitting 340.
To prevent the resilient contact piece 345 from losing the proper spring characteristic thereof, a stopper 348 has conventionally been provided. The front end of the stopper 348 is formed so as to confront the lower surface of the resilient contact piece 345 by bending a part of the lower wall plate 343 of the cylindrical insertion portion 341 upward.
This stopper 348 prevents excessive flexion of the resilient contact piece 345. That is, when the resilient contact piece 345 resiliently flexes, the lower surface of the resilient contact piece 345 is abutted against the front end of the stopper before the amount of flexion thereof exceeds the limit of resiliency thereof. As a result, resilient deformation of the resilient contact piece 345 more than such limit of resiliency is blocked, thereby preventing the excessive flexion of the resilient contact piece 345. Hence, the proper spring characteristic of the resilient contact piece 345 is maintained, and the male terminal fitting can come in contact with the female terminal fitting 340 reliably.
In the conventional female terminal fittings, for instance shown in FIGS. 19, 30, the former stoppers 60 project sideways by a bending margin g that is equal to the thickness of the resilient contact piece as shown in FIG. 20. Therefore, it is required that the width of the resilient contact piece 53 be smaller at least by a bending margin 2g within the limited width of the cylindrical insertion portion, and this in turn prevents the resilient contact piece 53 from having a large resiliency. If the stopper is bent so as not to project sideways by the bending margin g in FIG. 20, then the stopper must be bent by nicking the resilient contact piece in the width direction by the bending margin g, which also prevents the resilient contact piece 53 from having a large resiliency. As a result, particularly small resilient contact pieces have been useless because of their insufficient resiliency.
When the stopper 61 shown in FIG. 21, i.e., the stopper formed by cutting a part of the wall portion is applied to the resilient contact piece 53 that has the first and second folds 56, 57 shown in FIG. 6, the cylindrical insertion portion becomes fragile. Therefore, such design has not been applicable to particularly small resilient contact pieces.
Although provided with the reinforcing piece 105, the aforementioned conventional terminal fitting as shown in FIG. 23 is deformed when the force biasing the flexible tongue piece 104 is so large. As a result, the flexible tongue piece 104 flexes so excessively as to lose the sprint characteristic thereof. In addition, the reinforcing piece 105 is displaced due to a return ensuring the machining operation when formed by cutting and bending upward, and this makes it difficult to place the reinforcing piece 105 in correct position during fabrication.
Furthermore, the conventional stopper 61 as shown in FIG. 21 is formed by bending the thin plate substantially perpendicularly, so that a biasing force is applied to the plate edge thereof by the resilient contact piece 53. As a result, when a large biasing force is applied to the stopper 61, the stopper 61 may, in some cases, be so inclined as to lose the function thereof. Particularly, small-sized female terminal fittings have addressed the problem that the stopper thereof is easily inclined, because the material of which the stopper is made is thin.
The conventional method of blocking the excessive flexion of the resilient contact piece 345 by arranging the stopper 348 also has addressed the following problems.
When a foreign object is inserted into the cylindrical insertion portion with a large force, the stopper 348 may be broken while inclined by the biasing force from the resilient contact piece 345 side, or the resilient contact piece 345 made of a thin metal plate may be bent. Particularly, small-sized female terminal fittings 340, in which the metal strip used as a material is thin, are easy to cause such problem.
As a result, the resilient contact piece 345 is subjected to settling to lose the proper spring characteristic thereof or to hamper smooth insertion.
The present device has been made in consideration of the aforementioned circumstances.